Semiconductor Device, Electronic Component and Method

ABSTRACT

In an embodiment, a semiconductor device includes a galvanically isolated signal transfer coupler having a contact pad. The contact pad includes a metallic base layer, a metallic diffusion barrier layer arranged on the metallic base layer, and a metallic wire bondable layer arranged on the metallic diffusion barrier layer. The metallic diffusion barrier layer includes a first portion and a second portion. The first portion has a first surface and a second surface opposing the first surface. The first surface has a curved surface at the periphery. The first portion extends in a transverse plane and has a width. The second portion protrudes from the second surface intermediate the width of the first portion.

BACKGROUND

In some applications, two or more electric circuits communicate, forexample, by bidirectional signal exchange. If the electric circuits havea ground at different potentials, galvanic isolation may be used toprevent current flow between the electric circuits whilst permittingcommunication between the electric circuits. Galvanic isolation may bebased on optical, capacitive or inductive communication for example. Anexample of a device for inductive galvanic isolation and signal exchangeis a coreless transformer which includes a primary winding and asecondary winding separated by an isolation layer that is sufficientlythin to allow bidirectional transmission of signals.

In some applications in which electric power and information aretransferred from a higher-voltage network, such as the grid, to alower-voltage network, such as a domestic power supply network,reinforced galvanic isolation against spikes of up to 10 kV or higher isdesirable, if not required by regulatory authorities.

SUMMARY

In an embodiment, a semiconductor device includes a galvanicallyisolated signal transfer coupler including a contact pad. The contactpad includes a metallic base layer, a metallic diffusion barrier layerarranged on the metallic base layer, and a metallic wire bondable layerarranged on the metallic diffusion barrier layer. The metallic diffusionbarrier layer includes a first portion and a second portion. The firstportion has a first surface including a curved surface at the peripheryand a second surface opposing the first surface. The first portionextends in a transverse plane and has a width. The second portionprotrudes from the second surface intermediate the width of the firstportion.

In some embodiments, the semiconductor device further includes a firstisolation layer arranged on peripheral regions of the metallic baselayer and having a first opening exposing a portion of the metallic baselayer, wherein the second portion of the metallic diffusion barrierlayer is arranged in the first opening in the first isolation layer andthe first portion of the metallic diffusion barrier layer extends onto asurface of the first isolation layer adjacent the first opening.

In some embodiments, the semiconductor device further includes ametallic passivation layer on the metallic wire bondable layer.

In some embodiments, the metallic base layer includes copper, and/or themetallic diffusion barrier layer includes NiP, and/or the metallic wirebondable layer includes Pd and/or the metallic passivation layerincludes Au.

In some embodiments, the semiconductor device further includes a secondisolation layer arranged on peripheral regions of the metallic wirebondable layer and including a second opening exposing a portion of themetallic wire bondable layer. The metallic passivation layer may bearranged in and bounded by the second opening.

In some embodiments, the semiconductor device further includes a thirdisolation layer including a ring arranged on the first isolation layerand a fourth isolation layer arranged on outer faces of the thirdisolation layer.

In some embodiments, the first isolation layer includes hydrogenatedSi_(x)N_(y) and the second isolation layer includes an imide.

In some embodiments, the third isolation layer includes SiO_(x) orphosphosilicate glass and the fourth isolation layer includeshydrogenated Si_(x)N_(y).

In some embodiments, the galvanically isolated signal transfer couplerincludes an inductive coupler including a planar coil coupled to thecontact pad.

In some embodiments, the inductive coupler includes a second planar coilarranged in a stack with the first planar coil and galvanically isolatedfrom the first planar coil by a isolation layer including SiO_(x) and isconfigured to provide reinforced galvanic isolation for a surge pulseisolation voltage V_(IOSM) of at least 10 kV_(peak).

In some embodiments, the semiconductor device further includes a thirdplanar coil that is arranged substantially coplanar with the firstplanar coil and is coupled to the contact pad.

In some embodiments, the planar coil and the metallic base layer areintegrated in a semiconductor die.

In some embodiments, the galvanically isolated signal transfer couplerincludes a capacitive coupler and the contact pad provides a plate ofthe capacitive coupler.

In an embodiment, an electronic component includes the semiconductordevice according to any one of the previously described embodiments anda bidirectional signal transfer path coupled to the semiconductordevice. A galvanically isolated signal transfer coupler is coupled inthe bidirectional signal transfer path and is coupled by a bond wire tothe semiconductor device. The galvanically isolated signal transfercoupler provides reinforced galvanic isolation for a surge pulseisolation voltage V_(IOSM) of at least 10 kV_(peak).

In some embodiments, the electronic component further includes a furthersemiconductor device being coupled to the semiconductor device by way ofthe bidirectional signal transfer path.

In an embodiment, a method for forming a contact pad includes depositinga metallic diffusion barrier layer onto a surface of a metallic baselayer exposed in a first opening of a first isolation layer that coversa peripheral region of the metallic base layer such that the metallicdiffusion barrier layer extends onto an outer surface of the firstisolation layer. The metallic diffusion barrier layer is annealed and ametallic wire bondable layer is deposited onto the annealed metallicdiffusion barrier layer.

In some embodiments, the metallic diffusion barrier layer is depositedusing electro-chemical deposition or galvanic deposition.

In some embodiments, the method further includes depositing a secondisolation layer onto peripheral regions of the metallic wire bondablelayer defining a second opening exposing a portion of the wire bondablelayer.

In some embodiments, the method further includes depositing a metallicpassivation layer onto the metallic wire bondable layer such that thesecond isolation layer bounds the metallic passivation layer.

In an embodiment, a semiconductor device is provided that includes agalvanically isolated signal transfer coupler including a contact pad.The contact pad includes a metallic base layer and a metallic anchoringlayer arranged on the metallic base layer. The metallic anchoring layerincludes a first portion and a second portion. The first portion has afirst surface and a second surface opposing the first surface. The firstsurface of the first portion includes a curved surface at the periphery.The first portion extends in a transverse plane and has a width. Thesecond portion protrudes from the second surface intermediate the widthof the first portion.

In some embodiments, the metallic anchoring layer and/or the metallicbase layer includes copper.

In some embodiments, the semiconductor device further includes a firstisolation layer arranged on peripheral regions of the metallic baselayer and having a first opening exposing a portion of the metallic baselayer, wherein the second portion of the metallic anchoring layer isarranged in the first opening in the first isolation layer and the firstportion of the metallic anchoring layer extends onto a surface of thefirst isolation layer adjacent the first opening.

In some embodiments, the first isolation layer includes SiO_(x).

In some embodiments, the semiconductor device further includes ametallic adhesion promotion layer lining the first opening. In someembodiments, the semiconductor device further includes an insulatingpassivation layer arranged on the first surface of the metallicanchoring layer.

In some embodiments, the insulating passivation layer includes Al₂O₃ orSi_(x)N_(y). In some embodiments, the first isolation layer includesSi_(x)N_(y).

In some embodiments, the metallic anchoring layer is in direct contactwith the metallic base layer, the side walls of the first opening andsurface of the insulating layer adjacent the first opening.

In some embodiments, the semiconductor device further includes one ormore metallic layers arranged on the metallic anchoring layer.

In some embodiments, the one or more further metallic layers include aNiP layer arranged on an outer surface of the anchoring layer, a Pdlayer arranged on the NiP layer and a Au layer arranged on the NiPlayer.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The elements of the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding similarparts. The features of the various illustrated embodiments can becombined unless they exclude each other. Exemplary embodiments aredepicted in the drawings and are detailed in the description whichfollows.

FIG. 1a illustrates a semiconductor device including a galvanicallyisolated signal transfer coupler including a contact pad according to anembodiment.

FIG. 1b illustrates a semiconductor device including a galvanicallyisolated signal transfer coupler including an inductive couplerincluding a planar coil and a contact pad according to an embodiment.

FIG. 1c illustrates a semiconductor device including a galvanicallyisolated signal transfer coupler including a capacitive couplerincluding a contact pad according to an embodiment.

FIG. 2 illustrates a semiconductor device including an inductive couplerincluding planar coil and a contact pad according to an embodiment.

FIG. 3a illustrates a contact pad for an inductive or a capacitivecoupler.

FIG. 3b illustrates an enlarged view of the contact pad of FIG. 3 a.

FIG. 4 illustrates a connection structure for an inductive or acapacitive coupler according to an embodiment.

FIG. 5 illustrates a connection structure for an inductive or acapacitive coupler according to an embodiment.

FIG. 6a illustrates a contact pad for an inductive or a capacitivecoupler according to a further embodiment.

FIG. 6b illustrates a contact pad for an inductive or a capacitivecoupler according to a further embodiment.

FIG. 7 is a flow chart of a method for fabricating a contact pad for aninductive or a capacitive coupler.

FIG. 8a illustrates a perspective view of an inductive coupler accordingto an embodiment.

FIG. 8b illustrates a plan view of planar spiral coils for an inductivecoupler.

FIG. 8c illustrates a plan view of a planar spiral coil for an inductivecoupler.

FIG. 9a illustrates a schematic circuit diagram of a system including aninductive coupler providing galvanic isolation and signal transfer.

FIG. 9b illustrates a schematic circuit diagram of a system including acapacitive coupler providing galvanic isolation and signal transfer.

FIG. 10 illustrates a schematic diagram of a power conversion deviceincluding an inductive coupler providing galvanic isolation and signaltransfer.

FIG. 11 illustrates an electronic component including at least twosemiconductor devices with a bidirectional data exchange path includingan inductive coupler.

FIG. 12 illustrates a detailed view of the connection structure to thecontact pad of the inductive coupler of FIG. 11.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top”,“bottom”, “front”, “back”, “leading”, “trailing”, etc., is used withreference to the orientation of the figure(s) being described. Becausecomponents of the embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, thereof, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

A number of exemplary embodiments will be explained below. In this case,identical structural features are identified by identical or similarreference symbols in the figures. In the context of the presentdescription, “transverse” or “transverse direction” and “lateral” or“lateral direction” should be understood to mean a direction or extentthat runs generally parallel to the lateral extent of a semiconductormaterial or semiconductor carrier. The lateral direction thus extendsgenerally parallel to these surfaces or sides. In contrast thereto, theterm “vertical” or “vertical direction” is understood to mean adirection that runs generally perpendicular to these surfaces or sidesand thus to the lateral direction. The vertical direction therefore runsin the thickness direction of the semiconductor material orsemiconductor carrier.

As employed in this specification, when an element such as a layer,region or substrate is referred to as being “on” or extending “onto”another element, it can be directly on or extend directly onto the otherelement or intervening elements may also be present. In contrast, whenan element is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present.

As employed in this specification, when an element is referred to asbeing “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

Galvanic isolation in power equipment refers to an arrangement in whichan output power circuit is electrically and physically isolated from aninput power circuit to prevent current flow. Energy or information canstill be exchanged between the circuits by other means, such ascapacitance, induction or electromagnetic waves, or by optical, acousticor mechanical means. Galvanic isolation may be used where two or moreelectric circuits are to communicate, but their grounds are at differentpotentials, for example. Common reasons for providing galvanic isolationinclude safety from fault conditions in industrial grade products andapplications in which communication between devices is needed but eachdevice regulates its own power.

In some electronic systems, control functions are provided by lowervoltage circuitry that is galvanically isolated from high-powercircuitry. A bidirectional signal path between the lower-voltagecircuitry and the higher-voltage circuitry can be used, for example, totransmit control data from a system controller to a power supply and toreceive monitoring data from the power supply. When the high-powercircuitry defines a power supply, high-voltage electrical isolation fromearth or ground may be required for the power supply system by commonindustry practice or regulatory authorities. For reinforced galvanicisolation, examples of industry standards which may be referred to insuch practices and regulations include ICE-60747-5-5 or VDE0884-11. Forbasic galvanic isolation, an example of an industry standard which maybe referred to is IEC 60664-1 and VDE0884-11.

One way of providing a bidirectional signal path that provides galvanicisolation between higher-voltage circuitry and lower voltage circuitryis a transformer or inductive coupler in which the signal is transmittedinductively.

Embodiments described herein may be used to provide a connectionstructure for use in an inductive coupler and a device including atleast one coil of an inductive coupler with a contact pad which is morerobust in fault conditions and which may, when used, increase theoperational lifetime of the inductive coupler or device. An inductivecoupler may also be called a transformer. In some embodiments, thetransformer is a coreless transformer including a primary coil and asecondary coil that are positioned close enough together to facilitatereliable data exchange and which are sufficiently isolated from oneanother to provide galvanic isolation. The primary and secondary coilsmay be planar coils that are integrated into a semiconductor die whichmay include further circuitry.

A further way of providing a bidirectional signal path that providesgalvanic isolation between higher-voltage circuitry and lower voltagecircuitry is a capacitive coupler in which the signal is transmittedcapacitively.

Embodiments described herein may be used to provide a connectionstructure for use in a capacitive coupler. A capacitive coupler mayinclude two conductive plates separated by a dielectric. The twoconductive plates of the capacitive coupler may be integrated into asemiconductor die which may include further circuitry.

FIG. 1a illustrates a semiconductor device 20 including a galvanicallyisolated signal transfer coupler 21 including a contact pad 22 accordingto an embodiment. The galvanically isolated signal transfer coupler 21may enable bidirectional signal exchange and may include an inductivecoupler 23, as illustrated in the embodiment of FIG. 1b or a capacitivecoupler 24 as illustrated in the embodiment of FIG. 1 c.

The contact pad 22 includes a metallic base layer 25, a metallicdiffusion barrier layer 26 arranged on the metallic base layer 25 and ametallic wire bondable layer 27 arranged on the metallic diffusionbarrier 26. The metallic diffusion barrier layer 26 includes a firstportion 28 that has a first outer surface 29 including a curved surface30 at the periphery 31 and a second surface 32 opposing the firstsurface. The first portion 28 extends in a transverse plane and has awidth. The metallic diffusion barrier layer 26 further includes a secondportion 33 which protrudes from the second surface 32 intermediate thewidth of the first portion 28. The width of the first portion 28 refersto the width, x, of the first portion 28 in the transverse plane.

Since the second portion 33 protrudes from the second surface 32intermediate the width of the first portion 28, the second surface 32surrounds the second portion 33 on all sides at the junction between thefirst portion 28 and the second portion 29 or in other words, the firstportion 28 extends on all sides from the second portion 33. The lateralarea of the first portion 28 is greater than the lateral area of thesecond portion 33. The metallic diffusion barrier layer 26 has a shapewhich may be described as a mushroom-type shape with a head that has alateral area that is greater than a lateral area of a pin protrudingfrom the lower surface of the head.

The contact pad 22, in particular, the first portion 28 or head includesa periphery with an outer curved surface extending towards the secondsurface 32 and the second portion 33 or pin of the metallic diffusionbarrier layer 26. The curved surface of the periphery avoids thepresence of sharp edges at the outermost surface of the metallicdiffusion barrier layer 28 which may assist in increasing the robustnessof the galvanically isolated signal transfer coupler 21 to a faultcondition, for example a transient voltage spike, and may assist inincreasing the operational lifetime of the galvanically isolated signaltransfer coupler 21 and semiconductor device 20.

The central region of the first surface 29 may be substantially planarfor accepting the head of a bond wire connection for coupling thegalvanically isolated signal transfer coupler 21 to a circuit for signaltransmission or exchange. The periphery 31 of the first surface 29 ofthe first portion 28 may have a radius of curvature, r, which lieswithin the range 0.5 to 2 times the maximum height of the first portion28. The metallic wire bondable layer 27 may conformally cover the firstsurface 29 of the first portion 28 and may also have a substantiallyplanar central portion and curved surface at the periphery.

FIG. 1b illustrates a semiconductor device 20′ including thegalvanically isolated signal transfer coupler 21 in the form of aninductive coupler 23 including a planar coil 34 which is coupled to thecontact pad 22.

The inductive coupler 23 may also be called a transformer and may be acoreless transformer. The inductive coupler 23 may be used for providinginductive bidirectional data exchange in a device having reinforcedgalvanic isolation.

The planar coil 34 may include an outer end formed by the contact pad22. The metallic base layer 25 of the contact pad 22 may besubstantially coplanar with the windings of the planar coil 34 of theinductive coupler 21. In some embodiments, the planar coil 34 is aspiral planar coil which includes the contact pad 22 at its outer endand includes a second contact pad at its inner end, which is positionedat the centre of the spiral.

FIG. 1c illustrates a semiconductor device 20″ including thegalvanically isolated signal transfer coupler 21 in the form of acapacitive coupler including the contact pad 22. The contact pad 22forms a first plate 35 of a pair of plates 35, 36 providing a capacitor.The plates 35, 36 are spaced apart from one another by a dielectric 37.

In some embodiments, the first portion 28 of the metallic diffusionbarrier 26 of the contact pad 22 has a longitudinal axis extendingsubstantially perpendicular to the transverse plane of the first portion28 and the second portion 33 has a longitudinal axis which is alignedwith the longitudinal axis of the first portion 28. In theseembodiments, the second portion 33 may be concentric with the firstportion 28 such that the first portion extends laterally outwardly bysubstantially the same distance from the side faces of the secondportion 33. The contact pad 22 may be substantially circular in planview.

The metallic diffusion barrier layer 26 may provide a barrier againstdiffusion between the material of the wire bondable layer 27 and thematerial of the metallic base layer 25 as well as providing a size andshape for reducing the electric field at edges of the contact pad 22 inthe event of a voltage spike.

In some embodiments, the metallic base layer 25 may include copper, forexample high purity copper. In these embodiments, the metallic diffusionbarrier layer 26 may include nickel phosphorus and the metallic wirebondable layer 27 may include palladium. Palladium is suitable forforming a reliable low ohmic connection to wire bonds including gold oraluminium for example.

In embodiments including an inductive coupler 23, the planar coil 34 andthe metallic base layer 25 of the contact pad 22 may include copper, inparticular high purity copper.

In some embodiments, a further metallic passivation layer is arranged onthe metallic wire bondable layer 27. The metallic passivation layer maybe provided to prevent corrosion or oxidation of the metallic wirebondable layer 27, for example during storage before application of thebond wire to the contact pad 22. In the case of a wire bondable layerincluding palladium, the metallic passivation layer may include gold,for example.

In some embodiments, the wire bondable layer may be omitted and theouter surface of the metallic diffusion barrier 26 may provide a surfaceonto which a bond wire may be reliably attached.

In some embodiments, the metallic diffusion barrier layer 25 may includeNi, CoW or NiMoP.

In some embodiments, the contact pad includes a Cu anchoring layerhaving a size and shape corresponding to one of the embodiments of themetallic diffusion barrier layer 26. In the case of a copper metallicbase layer 25 and a copper anchoring layer, the copper anchoring layeris not required to have a metallic diffusion barrier function and so isbetter called an anchoring layer, since the mushroom-type form of thecontact pad may be used to provide mechanical anchoring of the contactpad with the surrounding passivation and insulating layers.

The contact pad 22 and, in particular, the shape of the metallicdiffusion barrier layer 26 may be formed by suitable selection andstructuring of passivation and/or isolation layers and depositiontechniques for depositing the contact pad 22 as is described withreference to FIG. 2.

FIG. 2 illustrates a schematic cross-sectional view of semiconductordevice 40 including an inductive coupler 41 including a planar coil 42coupled to a contact pad 43. The contact pad 43 includes a metallic baselayer 44 which is substantially coplanar with the planar coil 42, ametallic diffusion barrier layer 45 arranged on the metallic base layer44 and a metallic wire bondable layer 46 arranged on the metallicdiffusion barrier 45.

The inductive coupler 41 is integrated into a multilayer metallisationstructure 47 arranged on an upper surface 48 of a semiconductor die 49.The semiconductor die 49 may include silicon, for example single crystalsilicon and may include one or more low-voltage semiconductor devicesintegrated in the semiconductor die 49 which are not illustrated in theview of FIG. 2.

Reliability of the conductive connection from the inductive coupler 41to a further device or circuit under fault conditions may be improvedwith the assistance of an insulating passivation layer 50 arranged on anoutermost surface 51 of the metallisation structure 47 which covers theplanar coil 42 and peripheral regions of the metallic base layer 44. Thepassivation layer 50 includes an opening 52 above the metallic baselayer 44 of the contact pad 43. The metallic diffusion barrier layer 45is arranged in the opening 52 such that the opening 52 defines the sizeand shape of a lower portion 54 of the metallic diffusion barrier layer45. An upper portion 55 of the metallic diffusion barrier layer 45extends over the passivation layer 50 adjacent to the opening 52 andincludes a lateral area that is greater than a lateral area of the lowerportion 54. The planar coil 42 which is electrically coupled to thecontact pad 43 may be integrated within the metallisation structure 47arranged on the upper surface 48 of the semiconductor die 49.

The metallic diffusion barrier layer 45 may be fabricated using galvanicdeposition or electrochemical deposition such that the lower portion 54grows on the exposed surface of the metallic base layer 44 upwardly andafter filling the opening 52 in the passivation layer 54 continues togrow upwardly as well as outwardly such that a peripheral region 56 ofan upper portion 55 is positioned on the passivation layer 50 and suchthat the outer surface 57 has a curved surface in the peripheral region58.

The upper portion 55 of the metallic diffusion barrier layer 45 providesa first portion extending in a transverse plane and having a width wwhich has a first surface 57 and a second surface opposing the firstsurface 57. The first surface 57 includes a curved surface at theperiphery in the peripheral region 58. The lower portion 54 of themetallic diffusion barrier layer 45 provides a second portion thatprotrudes from the second surface of the first portion. The secondportion protrudes from the second surface at a position intermediate thewidth w of the first portion.

Curved outer surfaces such as the peripheral region 58 of the contactpad 43 are useful in high-voltage devices, for example. In someembodiments, the side face 66 of the metallic base layer 44 may alsohave a curved form. Furthermore, at least the outer surface 67 of theoutermost winding of the planar coil 42 and of the planar coil 60 mayalso have a curved form.

A metallic diffusion barrier layer including NiP may be fabricated usingelectrochemical deposition, CoW by electrochemical deposition, alsocalled electroless deposition, NiMoP by galvanic and electro chemicaldeposition, Ni by galvanic deposition, for example.

The metallic diffusion barrier 45 may fill the opening 54 in thepassivation layer 50 and cover the edge of the opening 54 at the uppersurface of the passivation layer 50. During the fabrication of theopening 54 in the passivation layer 50, material of the underlyingmetallic base layer 44 may be deposited on the side walls of the opening54 in the passivation layer 50. Such material may have an elongate orspike form with edges which, if not adequately covered with furtherconductive material, could provide a site for failure due to theformation of a locally increased electric field in a fault conditionsuch as a transient voltage spike. The shape of the metallic diffusionbarrier 45, which fills the opening 54 and neighbouring regions of theupper surface of the passivation layer 50 covers such material and maybe used to avoid the presence of such a site.

The passivation layer may include Si_(x)N_(y), in particularhydrogenated Si_(x)N_(y). The thickness of the passivation layer 50 maylie in the range of 0.5 μm to 5 μm and the size of the opening 54 maylie in the range of 50 μm to 120 μm.

As is illustrated in FIG. 2, in some embodiments, the inductive coupler41 may further include a second planar coil 60 which is arrangedunderneath the planar coil 42 and spaced apart from the planar coil 42by one or more dielectric or isolation layers 61. Some embodiments, thedielectric layer 61 may include silicon oxide. Both of the planar coils42, 60 may be integrated into the metallization structure 47 on thesemiconductor die 49.

In some embodiments, the planar coils 42, 60 and the metallic base layer44 may be fabricated by Damascene techniques. The metallisationstructure 47 may include a silicon nitride layer 62 and a silicon oxidelayer 63 such that the metallic planar coil 60 is positioned on thesilicon nitride layer 62 and embedded within the oxide layer 63. Thesilicon oxide layer 61 is arranged on the lower plane coil 60, a siliconnitride layer 64 is arranged on the silicon oxide layer 61 and a furthersilicon oxide layer 65 is arranged on the silicon nitride layer 64. Theplanar coil 41 and the metallic base layer 44 are arranged on thesilicon nitride layer 64 and embedded within the silicon oxide layer 65.The spacing between the planar coils 42, 60 and the material of thedielectric layer 61 may be selected such that the inductive coupler 41provides basic or reinforced galvanic isolation which fulfils therequirements of VDE 0884-11, IEC 60664-1 or IEC 62368, respectively.

FIG. 3a illustrates a cross-sectional view of a portion of amushroom-shaped contact pad 70 according to an embodiment, which may beused as the contact pad of an inductive coupler according to any one ofthe embodiments described herein. FIG. 3a illustrates the dimensionswhich may be adjusted so as to provide reinforced galvanic isolation forhigh voltage applications. FIG. 3b illustrates an enlarged view of anedge region of the contact pad 70.

The contact pad 70 includes a mushroom-shaped metallic diffusion barrierlayer 71 arranged on a planar metallic base layer 72. The metallic baselayer 72 may be part of metallization structure 74 arranged on an uppersurface 75 of the semiconductor die 76. The metallic base layer 72 mayhave a width w_(b). The contact pad 70 may be substantially circular inplan view such that the metallic base layer 72 and the metallicdiffusion barrier layer 71 are also substantially circular plan view. Inthese embodiments, the width w_(b) of the metallic base layer 72 maycorrespond to the diameter of the substantially circular metallic baselayer 72.

An electrically insulating passivation layer 73 is arranged on the uppersurface 77 of the metallisation structure 74 and on the periphery 78 ofthe metallic base layer 72. In some embodiments, a distance l₁ of theperiphery 78 of the metallic base layer 72 is covered by the passivationlayer 73. The passivation layer 73 defines an opening 79 exposing thecentral portion of the upper surface 80 of the metallic base layer 72 inwhich the metallic diffusion barrier layer 71 is arranged. The base ofthe metallic diffusion barrier 71 has a width w₂ corresponding to thewidth of the opening 79 in the passivation layer 73. The passivationlayer 73 may have a thickness t which defines the height of the secondportion 81 of the metallic diffusion barrier layer 71. The metallicdiffusion barrier layer 71 may have an overall height h. The firstportion 82 of the metallic diffusion barrier layer 71 may have a widthw₁ which is greater than the width w₂ of the second portion 81positioned within the opening 79 in the passivation layer 73. The firstportion 82 therefore extends from the opening 79 over the outermostsurface 83 of the passivation layer 73 by distance 12. The width w₁ ofthe first portion 82 of the metallic diffusion barrier is greater thanthe width w₂ of the second portion 81 and is less than the width w_(b)of the metallic base layer. In the case of substantially circularcontact pad 70, distance 12 corresponds to half of the difference in thewidth of the first portion 82 and the width of the second portion 81,i.e. l₂=(w₁−w₂)/2.

In order to achieve basic and/or reinforced galvanic isolation, therelationship between the thickness t of the passivation layer 73 and thelength l₁ of the periphery 78 of the metallic base layer 72 which iscovered by the passivation layer 73 may be suitably selected. In someembodiments, the ratio of t to l₁ lies in the range of 0.5 to 1, i.e.0.5≤t/l₁≤1.

Furthermore, the ratio of the overall height h of the metallic diffusionbarrier layer 71 to the extension l₂ may be selected such that it liesin the range of 1.5 to 2.5, i.e. 1.5≤h/l₂≤2.5. The periphery of thefirst portion 82 of the contact pad 70 includes a radius of curvature r.The ratio of the radius of curvature r to the height h of the metallicdiffusion barrier layer 71 may lie in the range of 0.5≤r/h≤2. The radiusof curvature r may be at least twice the thickness t of the passivationlayer 73, so that r>t/2. The height h of the metallic diffusion barrierlayer 71, radius of curvature r of the periphery of the first portion 82and the thickness t of the passivation layer 73 may be selected suchthat h≈t+r.

The metallic base layer 72 has a thickness t_(b). The radius ofcurvature r may be greater than a third of the thickness t_(b) of themetallic base layer 72 so that r≥t_(b)/3. The length l₁ of the periphery78 of the metallic base layer 72 which is covered by the passivationlayer 73, the radius of curvature r of the periphery of the firstportion 82 and the thickness t_(b) of the metallic base layer may beselected such that r/3<l₁<6t_(b).

As an example, the radius of curvature may lie in the range of 3 μm to 5μm, the width w_(b) may be around 100 μm, the width w₂ may be greaterthan 20 μm, typically 80 μm to 90 μm and the width w₁ is greater than w₂and less than w_(b) and may be around 85 μm to 98 μm. In someembodiments w₁=w₂+2r. The length l₁ may be around 10 μm. The length l₂may be around 3 μm. The height h may be around 5 μm. The metallic baselayer may have a thickness of around 3 μm.

Some embodiments provide a connection structure including a contact padhaving a mushroom-type shape and a bond wire. The connection structuremay be used to couple an inductive coupler or a capacitive coupler to acircuit or semiconductor device of a circuit to provide galvanicisolation and signal transmission.

As is indicated schematically by the dotted line 84 in the enlarged viewof FIG. 3b , the dimensions and the relationship between the dimensionsof the contact pad 70 may be adjusted so as to achieve a value of thevoltage at or near the surface of the contact pad 70 and of a bond wire83 attached to the contact pad 70 which is more uniform and has asmoother form in order to provide reinforced galvanic isolation for highvoltage applications. The dimensions and the relationship between thedimensions may be adjusted in order that the value of the voltage at ornear the surface of the contact pad 70 and the bond wire 83 is asconstant as possible.

FIG. 4 illustrates a connection structure 90 including a contact pad 91and a bond wire 92 arranged on, and electrically coupled with, thecontact pad 91. The connection structure 90 may be used for inductivebidirectional data exchange in a device having reinforced galvanicisolation. For example, the connection structure 90 may be used in aninductive coupler, including an inductive coupler according to one ofthe embodiments described herein, or in a capacitive coupler, includinga capacitive coupler according to one of the embodiments describedherein.

The contact pad 91 includes a metallic base layer 93, a metallicdiffusion barrier layer 97 arranged on an upper surface 98 of themetallic base layer 93, a wire bondable layer 99 arranged on themetallic diffusion barrier layer 97 and a metallic passivation layer 100arranged on the metallic wire bondable layer 99. In particular, afterwire bonding, the metallic passivation layer 100 is arranged on the wirebondable layer 99 in regions outside of contact area between the head101 of the bond wire 92 and the metallic wire bondable layer 99.

The metallic base layer 93 may be positioned in an insulating layer ofthe metallisation structure 94 positioned on a surface of asemiconductor die which cannot be seen in the view of FIG. 4. Inparticular, the lower surface 95 and side faces 96 of the metallic baselayer 93 may be embedded in a dielectric layer or passivation layer ofthe metallisation structure 94. In some embodiments, the side faces 96of the metallic base layer 93 may have a rounded form.

The connection structure 90 may also include a first passivation layer102 arranged on an upper surface 103 of the metallisation structure 94and on peripheral regions of the upper surface 98 of the metallic baselayer 93. The passivation layer 102 includes an opening 104 which ispositioned above the central region of the upper surface 98 of themetallic base layer 93. The lower portion of the metallic diffusionbarrier layer 97 is arranged in this opening 104 and extends over theupper surface 105 of the passivation layer 102 such that the outersurface 106 of the metallic diffusion barrier layer 97 has a curved format the periphery 107 and is substantially planar in the region above theopening 104. The central substantially planar region 108 is suitable forproducing a good mechanical and electrical connection between the head101 of the bond wire 92 and the contact pad 91.

The metallic diffusion barrier layer 97 includes a mushroom-type shapeso that the upper portion has a larger area than the lower portion. Thecontact pad 91 may be substantially circular in plan view. The wirebondable layer 99 is arranged on the upper surface of the metallicdiffusion barrier layer 97 and conforms to the curved surface of theperiphery 107 such that the outer surface of the wire bondable layer 99also has a curved form, and curves in the direction of the metallic baselayer 93 in its peripheral region. The wire bondable layer 99 may be incontact with the upper surface 105 of the passivation layer 102laterally adjacent the opening 104.

The connection structure 90 includes a second isolation layer 109 whichis arranged on the upper surface 105 of the passivation layer 102 andhas a lateral extent such that it extends over the peripheral region 107of the metallic diffusion barrier layer 97 and in particular onto theperipheral regions of the wire bondable layer 99. The second isolationlayer 109 defines an opening 110 exposing the central portion of thewire bondable layer 99. The metallic passivation layer 100 is arrangedin this opening 110 and therefore has a lateral extent which is lessthan the lateral extent of the metallic wire bondable layer 99.

The materials of the various elements of the connection structure 90 maybe selected so as to provide particular properties. In an embodiment,the metallic base layer 93 includes copper, in particular high puritycopper. The wire bondable layer 99 includes palladium. In order toprevent diffusion between the palladium 99 of the wire bondable layer 99and the copper of the metallic base layer 93, the metallic diffusionbarrier layer 97 may include nickel phosphorus, i.e. a nickelphosphorous alloy. The metallic passivation layer 100 may include gold,for example. The bond wire 92 may include gold or aluminium or Cu or afurther metal or alloy capable of forming a low ohmic contact withpalladium 99. The interface region between the head 101 of the bond wire92 and the wire bondable layer 99 may be free of the metallicpassivation layer 100.

The first passivation layer 102 may include hydrogenated silicon nitrideso as to encourage charge trapping in the passivation layer and thesecond isolation layer 109 may include an imide, for example polyimide.An imide is useful since it adheres better to the palladium of the wirebondable layer 99 than to copper or nickel phosphorus and, therefore, tothe metallic diffusion barrier layer 97 and the metallic base layer 93.

The thickness and materials of the passivation layer 102 and secondisolation layer 109 may be selected to provide suitable level ofisolation between the bond wire 92 and further devices within thesemiconductor die.

After formation of the bond wire connection, the contact pad 91 and bondwire 92 may be encapsulated in a mold compound. The arrangement of thesecond isolation layer 109 covering the interface between thepassivation layer 102 and the metallic diffusion barrier layer 97 andthe better adhesion between the second isolation layer 109 and metallicwire bondable layer 99, may be used to hinder or prevent penetration ofmoisture from the overlying mold compound into this interface and reducethe likelihood of failure during a fault due to evaporation of moistureaccumulated at this interface.

FIG. 5 illustrates a connection structure 120 which may be used forinductive or capacitive bidirectional data exchange in a device havingreinforced galvanic isolation and in particular, reinforced galvanicisolation for sporadic, transient overvoltages and/or other interferencevoltages which may be caused by a lightning strike or other faultcircuit for example. The connection structure may be used in a devicehaving galvanic isolation rated for a 3 kV or 10 kV pulse.

The interconnection structure 120 differs from the interconnectionstructure 90 illustrated in FIG. 4 in the arrangement of the additionalisolation layers 121, 122 which increases the total thickness of theisolation layers in regions adjacent the contact pad 91 and bond wire92.

The connection structure 120 includes a contact pad 91 and a bond wire92 having a similar structure to that illustrated in FIG. 4. The contactpad 91 includes the metallic base layer 93, the metallic diffusionbarrier layer 97, the metallic wire bondable layer 99 and the metallicpassivation layer 100. The connection structure also includes thepassivation layer 102 arranged on the upper surface 103 of themetallisation structure 94 and in the peripheral regions of the uppersurface 98 of the metallic base layer 93 and second isolation layer 109.

The connection structure 120 further includes a third isolation layer121 which is arranged on the passivation layer 102 adjacent to theopening 104 and under the second isolation layer 109. The thirdisolation layer 121 may have the form of a ring which is substantiallyconcentric with the opening 104 and with the contact pad 91. The thirdisolation layer 121 is arranged at a distance from the side faces 96 ofthe metallic base layer 93. A fourth isolation layer 122 is arranged onthe upper surface 123 and side faces 124 of the third isolation layer121 and extends over the upper surface 105 of the passivation layer 102to the opening 104 in the passivation layer 102.

The fourth isolation layer 122 also defines an opening 126 which mayhave substantially the same lateral area as the opening 104. The upperportion of the metallic diffusion barrier layer 97 is positioned on thefurther isolation layer 122 in regions immediately adjacent to theopening 126. The wire bondable layer 99 also extends over the curvedside faces of the upper portion of the metallic diffusion barrier layer97 and is in contact with the fourth isolation layer 122. The secondisolation layer 109 is arranged on the fourth isolation layer 122 and onthe peripheral regions of the wire bondable layer 99 as in theconnection structure 90 illustrated in FIG. 4. After formation of thebond wire connection, the metallic passivation layer 100, bond wire 92and second isolation layer 109 may be encapsulated in a mold compound.

The passivation layer 102 may include hydrogenated Si_(x)N_(y) and havea thickness of 2 μm and the second isolation layer an imide and have athickness of 3 μm to 12 μm. The third isolation layer 121 may includephosphosilicate glass (PSG) or SiO_(x) and may have a thickness of 3 μmto 12 μm, typically 7 μm. The fourth isolation layer 122 may includehydrogenated Si_(x)N_(y) and may have a thickness of 300 nm. The opening110 in the second isolation layer 109 may have a diameter in the rangeof 50 μm to 120 μm.

As an example, for a nailhead bond connection, the bond wire 92 may havea diameter of 25 μm to 30 μm and the head 101 of the bond wire 92 adiameter of around 60 μm and a height of around 30 μm.

FIGS. 6a and 6b illustrate a contact pad 130 according to alternativeembodiments. The contact pad 130 includes a metallic anchoring layer 131arranged on a metallic base layer 132. The metallic base layer 132 andthe anchoring layer 131 may include Cu. The anchoring layer 131 has asize and shape corresponding to one of the embodiments of the metallicdiffusion barrier layer and has a mushroom-type form with an upperportion with a greater lateral area than a lower portion. The upperportion has a periphery with a curved form, curving in the direction ofthe lower portion. The position and volume of the lower portion isdefined by an opening in an insulation layer 134 which covers peripheralregions of a metallic base layer 132.

In the case of a copper metallic base layer 132 and a copper anchoringlayer 131, the anchoring layer 131 is not required to have a metallicdiffusion barrier function and so is better called an anchoring layer,since the mushroom-type form of the contact pad 130 may be used toprovide mechanical anchoring of the contact pad 130 with the surroundingpassivation and/or insulating layers 134. The contact pad 130 may beused in a galvanically isolated signal transfer coupler 135 in the formof an inductive coupler or a capacitive coupler.

The anchoring layer 131 may be treated after deposition by wet etching,for example, to produce the curved form at the periphery of the upperportion.

In the embodiment illustrated in FIG. 6a , the insulating layer 134includes SiO_(x) and contact pad 130 may include an adhesion promotionlayer 136, which is arranged on the exposed portion of the upper surface137 of the metallic base layer 132, on the side walls of the opening 138in the insulating layer 134 and on regions of the upper surface 139 ofthe insulting layer 134 adjacent the opening 138. The upper portion 140of the anchoring layer 131 is arranged on and extends outwardly from theadhesion promotion layer 136. The lower portion 141 of the anchoringlayer 131 fills the opening 138. An insulating passivation layer 142,for example a layer of Al₂O₃ or Si_(x)N_(y) having a thickness of notmore than a few atoms, may be arranged on the outermost surface of thecontact pad 130. The insulating passivation layer 142 may cover theupper surface 139 of the insulating layer 134, side face of the adhesionpromotion layer 136 and free lying outer surfaces 143 of the anchoringlayer 131.

In the embodiment illustrated in FIG. 6b , the insulating layer 134includes Si_(x)N_(y) and the anchoring layer 131 is in direct contactwith the upper surface 137 of the metallic base layer 132, the sidewalls of the opening 138 and the upper surface 139 of the insulatinglayer 134. The contact pad 130 further includes one or more layersarranged on the outer surface of the anchoring layer. In someembodiments, a NiP layer 143 is arranged on the outer surface 146 of theanchoring layer 131, a Pd layer 144 on the NiP layer 143 and a Au layer145 on the NiP layer 144.

The upper portion 140 of the anchoring layer 131 provides a firstportion having an outer surface 146 or first surface and a secondsurface opposing the first surface. The first surface of this firstportion has a curved surface at the periphery. The first portion extendsin a transverse plane and has a width. The lower portion 141 of theanchoring layer 131 provides a second portion protruding from the secondsurface of the first portion intermediate the width of the firstportion.

FIG. 7 illustrates a flow chart 150 of a method for fabricating acontact pad which may be used for an inductive coupler providingbidirectional signal exchange and basic and/or reinforced galvanicisolation.

In box 151, a metallic diffusion barrier layer is deposited onto asurface of a metallic base layer exposed in an opening of a firstisolation layer that covers a peripheral region of the metallic baselayer such that the metallic diffusion barrier layer extends onto anouter surface of the first isolation layer. In box 152, the metallicdiffusion barrier layer is annealed. In box 153, a metallic wirebondable layer is deposited onto the annealed metallic diffusion barrierlayer.

The metallic diffusion barrier layer is annealed before the depositionof the subsequent metallic layer or layers. This method may be used sothat the subsequently deposited layer can provide a seal for any gapthat may be formed between the metallic diffusion barrier and theopening in the first isolation layer that may arise due to relaxationand contraction of the metallic diffusion barrier layer duringannealing.

The outer surface of the metallic diffusion barrier may have a curvedform at its periphery and extend towards the first isolation layer. Thecentral position of the metallic diffusion barrier layer which isbounded by the periphery may be substantially planar.

The metallic diffusion barrier layer may be deposited usingelectro-chemical deposition or galvanic deposition depending on thecomposition. A NiP metallic diffusion barrier layer may be depositedusing electro-chemical deposition. An external power source is used ingalvanic deposition, whereas no external power source is used inelectro-chemical deposition. Electro-chemical deposition is alsoreferred to as electroless deposition. These methods may be used toproduce an outer surface having a curved form at the periphery due tothe growth mechanism of the metallic diffusion barrier on the firstisolation layer in regions adjacent to the opening.

The metallic wire bondable layer may be deposited galvanically or byelectroless deposition depending on the composition. For example, Pd maybe deposited by electroless deposition and Ni by galvanic deposition.The wire bondable layer may conform to the shape of the underlyingmetallic diffusion barrier layer and also have a curved form at itsperiphery.

In some embodiments, a second isolation layer is deposited ontoperipheral regions of the metallic wire bondable layer. The secondisolation layer may include a material that has good adhesive propertiesto the wire bondable layer and/or better adhesive properties to the wirebondable layer compared to the metallic diffusion barrier layer. Thisarrangement may be used to prevent delamination of the second isolationlayer from the conductive contact pad.

In some embodiments, a metallic passivation layer is deposited onto themetallic wire bondable layer such that the second isolation layerdefines the lateral extent of the metallic passivation layer. Themetallic passivation layer has a lateral extent that is less than thelateral extent of the underlying metallic wire bondable layer and headof the metallic diffusion barrier layer, since the second isolationlayer is arranged on the peripheral region of the wire bondable layer.The metallic passivation layer may be used to hinder oxidation orcontamination of the wire bondable layer during production and storage,in particular, before a wire bond is attached to the contact pad. Themetallic passivation may not form a part of the bond between the wirebond and the contact pad.

A connection structure can be formed by applying a bond wire to thesubstantially planar central portion of the contact pad, for exampleusing a nail head wire bonding technique.

FIG. 8a illustrates a perspective view of an example of an inductivecoupler 160 which may be coupled to a circuit by the connectionstructure according to one of the embodiments described herein toprovide galvanic isolation. The inductive coupler 160 may also be usedin the device according to one of the embodiments descried herein.

The inductive coupler 160 includes a primary side 161 and a secondaryside 162 whereby each of the primary side 141 and secondary side 162includes at least one planar coil. In the embodiment illustrated in FIG.7a , each of the primary side 161 and the secondary side 162 includestwo substantially coplanar spiral planar coils 163, 164; 168, 169. Thesecondary side 161 includes a contact pad 165 arranged in the centre ofthe spiral planar coil 163, a contact pad 166 which is arranged betweenand coupled to the outer end of the two spiral planar coils 163 and 164and a contact pad 167 which is arranged in the centre of the spiralplanar core 164.

The shape and structure of the contact pad according to one of any oneof the embodiments described herein may be used for the central pad 166,whereby the metallic base layer is coplanar with and coupled to theplanar coils 163, 164. In some embodiments one or both of contact pads165, 167 also includes a structure according to any one of theembodiments described herein. The shape, size and structure of thecontact pads 165, 167 may be the same as that of the contact pad 166 ordifferent.

The primary side 164 also includes two coplanar spiral planar coils 168,169 which are positioned underneath and spaced apart by a dielectriclayer 170 from the respective spiral planar coil 163, 164 of thesecondary side 162. The planar coils 168, 169, 163, 164 are electricallyconductive and may be integrated on a silicon chip and, in particular,in differing layers of a multilayer metallisation structure. The spiralplanar coils 163, 164, 168, 169 may include high purity copper and befabricated using Damascene techniques, for example.

However, in other embodiments, the inductive coupler may include asingle coil in the primary side 161 and a single coil in the secondaryside 162. The planar coil or coils need not be spiral and need not besubstantially circular.

FIGS. 8b and 8c illustrate further embodiments of planar spiral coilswhich may be used for the primary or secondary side of an inductivecoupler.

FIG. 8b illustrates an embodiment of an inductive coupler 160′ includingtwo planar spiral coils 171, 172, whereby a contact pad 173, 174 isarranged at the centre of each of the two planar spiral coils 171, 172and the two planar spiral coils 171, 172 are coupled by a substantiallyS-shaped connection. The two planar spiral coils 171, 172 may besurrounded by a continuous conductive isolation coil 175.

FIG. 8c illustrates an embodiment of an inductive coupler 160″ includinga single planar spiral coil 176, whereby a first contact pad 177 isarranged at the centre of the planar spiral coil 176 and a secondcontact pad 178 is arranged at the outer end of the planar spiral coil177. The planar spiral coil 176 and contact pads 177, 178 may besurrounded by a continuous conductive isolation coil 179.

The device including the inductive coupler or capacitive coupler and theconnection structure according to any one of the embodiments describedherein may be used to provide galvanic isolation, such as basic galvanicisolation or reinforced galvanic isolation in various applications andcircuits.

FIG. 9a illustrates a schematic view of a system 180 including a firstcircuit 181, a second circuit 182 and galvanic isolation provided by aninductive coupler 183. The inductive coupler 183 includes a first coil184 electrically coupled to the first circuit 181 and a second coil 165electrically coupled to the second circuit 182 and galvanic isolation186 arranged between the first coil 184 and the second coil 185.

The first circuit 181 and the second circuit 182 of the system 180 mayinclude a single device or two or more devices forming a circuit. Theinductive coupler 183 may include one or two coils on the primary sideand the secondary side. The system 180 may be used for power conversionso that the circuits 181, 182 may include a power conversion system anda driver circuit, for example.

FIG. 9b illustrates a schematic view of a system 190 including a firstcircuit 191, a second circuit 192 and galvanic isolation provided by twocapacitive couplers 193, 194. The first circuit 191 may be a highvoltage circuit and the second circuit 192 a low voltage circuit.Alternatively, both the first circuit 191 and the second circuit 192 maybe high voltage circuits or the first circuit 191 may be a low voltagecircuit and the second circuit 192 may be a high voltage circuit.

Each capacitive coupler 193, 194 includes two conductive plates 195,196; 195′, 196′ galvanically separated from one another by a dielectricmaterial 197; 197′. The dielectric material 197; 197′ has a dielectricstrength that is sufficiently high such that the required level ofgalvanic isolation, for example basic or reinforced, is provided. Forexample, the dielectric layer 197 can withstand a plate-to-plate voltagedifference of 5 kV_(R)m without suffering dielectric breakdown.

The capacitive coupler utilizes changes in capacitance to transmitsignals. In operation, the first circuit 191 transmits data to secondcircuit 192 by encoding the data, and then placing encoded data signalsin the form of pulses, RF waveforms, or glitches onto the plate 195. Thesignals are capacitively coupled to low-voltage plate 196, and are thendetected and decoded by the second circuit 192.

In the systems of FIGS. 9a and 9b , the primary and secondary sides aregalvanically isolated from the other and connected only through theinductive or capacitive couplers. The system may have the capability toprovide bi-directional data between the primary side and the secondaryside. In addition, power may be provided to the secondary side from theprimary side. The primary side may drive the secondary side through oneor more drivers (not illustrated) and the secondary side may providedata for sensing to the primary side.

FIG. 10 illustrates a schematic diagram of example of a powersemiconductor module 200 which may include the inductive coupler and/orconnection structure according to one or more of the embodimentsdescribed herein. The power semiconductor module 200 may include acapacitive coupler in place of the inductive coupler. The module 200 hasthree blocks 201, 202, 203. Block 201 includes one or more drivercircuits which may be integrated into a semiconductor driver component204. Block 202 includes a power section which may include two or moresemiconductor switches 205, 206, such as power transistors, which may becoupled to provide a half-bridge circuit, for example.

Block 203 ensures galvanic isolation between the driver circuit 201 andthe power section 202. The galvanic isolation can be integrated in thedriver component 204 or be formed by a separate component. The galvanicisolation may be provided by an inductive coupler 207 having a contactpad according to one of the embodiments described herein. The inductivecoupler may be coupled to the driver component 204 by a connectionstructure according to one of the embodiments described herein. Thedrive circuit 201 may be coupled to a further control unit 208 which isexternal to the module 200.

FIG. 11 illustrates an example of an electronic component 210 includinga first semiconductor die 211, a second semiconductor die 212 and atleast one inductive coupler 213 according to one of the embodimentsdescribed herein which provides reinforced galvanic isolation. FIG. 12illustrates the more detailed view of a portion of the inductive coupler213 of FIG. 12 and in particular, the bond wire connections 214 to thecontact pads 215, 216.

The inductive coupler 213 is coupled in the bidirectional signalexchange path between the first semiconductor die 211 and the secondsemiconductor die 212. In the embodiment illustrated in FIG. 11, theinductive coupler 213 has the structure illustrated in FIG. 8 a.

The first semiconductor die 211 is arranged on a first die pad 217 andthe second semiconductor die 212 is arranged on a second die pad 218.The second die pad 218 is spaced apart from the first die pad 217 andisolated therefrom by the mold compound 219 providing the housing 220 ofthe semiconductor component 210.

The inductive coupler 213 is integrated into the metallization structure221 arranged on the upper surface of the second semiconductor die 212.The inductive coupler 213 is electrically coupled so as to provide asignal path between the first semiconductor die 211 and the secondsemiconductor die 212 by bond wires 214.

The contact pad 215 which is coupled to the outer end of the two spiralplanar coils 223, 224 of the inductive coupler 213 may have a structureaccording to one of the embodiments described herein and, in particular,may have a rounded or curved periphery.

The first semiconductor die 211 may include a logic, operation amplifieror a Schmitt trigger circuit and the second semiconductor die 212 mayinclude a gate driver, or ADC (Analogue Digital Converter) circuit withSchmitt trigger.

Spatially relative terms such as “under”, “below”, “lower”, “over”,“upper” and the like are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the device in additionto different orientations than those depicted in the figures. Further,terms such as “first”, “second”, and the like, are also used to describevarious elements, regions, sections, etc. and are also not intended tobe limiting. Like terms refer to like elements throughout thedescription.

As used herein, the terms “having”, “containing”, “including”,“comprising” and the like are open ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise. It is to be understood that the features of thevarious embodiments described herein may be combined with each other,unless specifically noted otherwise.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A semiconductor device, comprising: agalvanically isolated signal transfer coupler comprising a contact pad,wherein the contact pad comprises: a metallic base layer; a metallicdiffusion barrier layer arranged on the metallic base layer; and ametallic wire bondable layer arranged on the metallic diffusion barrierlayer, wherein the metallic diffusion barrier layer comprises: a firstportion having a first surface and a second surface opposing the firstsurface, the first surface having a curved surface at a periphery, thefirst portion extending in a transverse plane and having a width; and asecond portion protruding from the second surface intermediate the widthof the first portion.
 2. The semiconductor device of claim 1, furthercomprising a first isolation layer arranged on peripheral regions of themetallic base layer and having a first opening exposing a portion of themetallic base layer, wherein the second portion of the metallicdiffusion barrier layer is arranged in the first opening in the firstisolation layer, and wherein the first portion of the metallic diffusionbarrier layer extends onto a surface of the first isolation layeradjacent the first opening.
 3. The semiconductor device of claim 1,further comprising a metallic passivation layer on the metallic wirebondable layer.
 4. The semiconductor device of claim 3, wherein at leastone of: the metallic base layer comprises copper; the metallic diffusionbarrier layer comprises NiP; the metallic wire bondable layer comprisesPd; and the metallic passivation layer comprises Au.
 5. Thesemiconductor device of claim 3, further comprising a second isolationlayer arranged on peripheral regions of the metallic wire bondable layerand comprising a second opening exposing a portion of the metallic wirebondable layer.
 6. The semiconductor device of claim 5, wherein themetallic passivation layer is arranged in and bounded by the secondopening.
 7. The semiconductor device of claim 5, further comprising athird isolation layer comprising a ring arranged on the first isolationlayer and a fourth isolation layer arranged on outer faces of the thirdisolation layer.
 8. The semiconductor device of claim 7, wherein thefirst isolation layer comprises hydrogenated Si_(x)N_(y), the secondisolation layer comprises an imide, the third isolation layer comprisesSiO_(x) or phosphosilicate glass, and the fourth isolation layercomprises hydrogenated Si_(x)N_(y).
 9. The semiconductor device of claim1, wherein the galvanically isolated signal transfer coupler comprisesan inductive coupler comprising a planar coil coupled to the contactpad.
 10. The semiconductor device of claim 9, wherein the inductivecoupler comprises a second planar coil arranged in a stack with thefirst planar coil and galvanically isolated from the first planar coilby an isolation layer comprising SiO_(x) and is configured to providereinforced galvanic isolation for a surge pulse isolation voltageV_(IOSM) of at least 10 kV_(peak).
 11. The semiconductor device of claim10, further comprising a third planar coil arranged substantiallycoplanar with the first planar coil and coupled to the contact pad. 12.The semiconductor device of claim 9, wherein the planar coil and themetallic base layer are integrated in a semiconductor die.
 13. Thesemiconductor device of claim 1, wherein the galvanically isolatedsignal transfer coupler comprises a capacitive coupler, and wherein thecontact pad provides a plate of the capacitive coupler.
 14. Anelectronic component, comprising: a semiconductor device comprising agalvanically isolated signal transfer coupler comprising a contact pad;wherein the contact pad comprises: a metallic base layer; a metallicdiffusion barrier layer arranged on the metallic base layer; and ametallic wire bondable layer arranged on the metallic diffusion barrierlayer, wherein the metallic diffusion barrier layer comprises: a firstportion having a first surface and a second surface opposing the firstsurface, the first surface of the first portion having a curved surfaceat the periphery, the first portion extending in a transverse plane andhaving a width; and a second portion protruding from the second surfaceintermediate the width of the first portion; and a bidirectional signaltransfer path coupled to the semiconductor device; wherein thegalvanically isolated signal transfer coupler is coupled in thebidirectional signal transfer path, is coupled by a bond wire to thesemiconductor device and provides reinforced galvanic isolation for asurge pulse isolation voltage V_(IOSM) of at least 10 kV_(peak).
 15. Theelectronic component of claim 14, further comprising a furthersemiconductor device coupled to the semiconductor device by thebidirectional signal transfer path.
 16. A method for forming a contactpad, the method comprising: depositing a metallic diffusion barrierlayer onto a surface of a metallic base layer exposed in a first openingof a first isolation layer that covers a peripheral region of themetallic base layer such that the metallic diffusion barrier layerextends onto an outer surface of the first isolation layer; annealingthe metallic diffusion barrier layer; and depositing a metallic wirebondable layer onto the metallic diffusion barrier layer after theannealing.
 17. The method of claim 16, further comprising: depositing asecond isolation layer onto peripheral regions of the metallic wirebondable layer defining a second opening exposing a portion of the wirebondable layer.
 18. The method of claim 17, further comprising:depositing a metallic passivation layer onto the metallic wire bondablelayer such that the second isolation layer bounds the metallicpassivation layer.
 19. A semiconductor device, comprising: agalvanically isolated signal transfer coupler comprising a contact pad,wherein the contact pad comprises: a metallic base layer; and a metallicanchoring layer arranged on the metallic base layer, and wherein themetallic anchoring layer comprises: a first portion having a firstsurface and a second surface opposing the first surface, the firstsurface of the first portion having a curved surface at the periphery,the first portion extending in a transverse plane and having a width;and a second portion protruding from the second surface intermediate thewidth of the first portion, wherein the metallic anchoring layer and/orthe metallic base layer comprises copper.
 20. The semiconductor deviceof claim 19, further comprising a first isolation layer arranged onperipheral regions of the metallic base layer and having a first openingexposing a portion of the metallic base layer, wherein the secondportion of the metallic anchoring layer is arranged in the first openingin the first isolation layer, and wherein the first portion of themetallic anchoring layer extends onto a surface of the first isolationlayer adjacent the first opening and an insulating passivation layerarranged on the first surface of the metallic anchoring layer.
 21. Thesemiconductor device of claim 20, wherein the metallic anchoring layeris in direct contact with the metallic base layer, side walls of thefirst opening and a surface of the insulating layer adjacent the firstopening.